Serene means extremely content or peaceful.
'content' is the French word for satisfied, happy
Black soil has the maximum content and is extremely fertile.
Something extremely nauseous and terrible.
A town that is extremely bustling and busy.
Extremely worn and in poor condition.
merutseh (מרוצה) = content or satisfied.
The French adjective "content" (fem. "contente") means "happy" or "satisfied", just like in English.
extremely beautiful; entrancingit means astonishing
Extremely or excessively cautious. A common fault these days.
The French word "content / contente" = 'happy'the English word 'content' = "le contenu"
It is possible that you are thinking of the word noxious, meaning extremely bad or toxic.
yes it is extremely rude, never say it.